End-on phototube



:Suvcntor ,pletely a photosensitive surface.

The particular phototube, which we have disclosed, is of thetransmission type photoelectric "surface That is, the design of the tubeis such that light passes through the Window I2 and lm I4 to effect aphotoelectric discharge. When a difference of potential is establishedbetween the cathode I and anode I8, the photoemission passes to theanode I8 from the photosensitive cathode surface I4. The phototube maybe connected into an appropriate circuit whereby the loutput current ofthe tube may be utilized as def Y lin that they could not escape intothe interelectrode space ibetween the cathode I2 andthe anode IS. On theother hand, if most of the light were allowed to vpass through thephotosensitive layer, very little, if any, light would lbe absorbed, toprovide energy for photoelectric emission. We

y have found that from 20% t0 50% of the light falling upon the windowI2 should be transmitted by the-photosensitive film I4.

In constructing our tube other materials may be used for thephotoelectric surface. Instead of using an antimony layer, eitherarsenic or bisanuth may be substituted, or if desired some other jalkali metal may replace the caesium; nor should our invention belimited to this particular type of photosensitive material as it isobvious that other photosensitive lms such as a silver-silveroxidecaesium surface may be used.

From the following description it is obvious that certain novel andadvantageous features lexist in this tube. The head of the tube whichgis the end closed by the glass window I2 is com- That is, the Lhead-onview of the tube is all photosurface which provides a large photocathodesurface relative to the cross-sectional dimensions of the tube.,Furthermore, by utilizing an envelope comprising the cathode cylinderID, it is unnecessary to use an enclosing glass envelope. This permits amuch smaller overall cross-sectional area of the tube and also allowsthe circuit leads to be connected directlyv to the cathode instead ofrequiring a conventional base structure. The

copper anode tube I8 is used .both as an electrode and asV an exhausttubulation 22. This provides a large electrode surface for collectingthe photoelectric current and also eliminates additional structureswhich would be required in a conventional tube for tube exhaust. Thelargerano'de tube also provides easier glass-to-metal sealing.

The important dimension of the tube is obviously its cross-sectionaldimension which in this case is determined fby the size of thephotosensitive cathode. This dimension of the cathode structure can bekept small relative to the corresponding dimension of conventionalphototubes.

Due to this small head-on dimension which is the part of the tubepresented to an activating beam of light, greater utility of the tube isevident. Machines which would utilize a series or a bank of such tubesmay be designed to much smaller overall dimensions than were formerlypossible. Due to its small size this tube may be incorporated ininstruments of small design where previously the use of .phototubesgreatly .complicated the technical problems at hand.

While certain specific embodiments have been illustrated and described,it will be understood that various changes and modifications may be madetherein without departing from the spirit and scope of the invention.

What we claim as new is:

1. A photoelectric tube including an envelope, said envelope comprisingan insulating tubular member, a metal tubular member coaxially sealed toone end of said insulating tubular member and a glass disc closing saidmetal tubular member, a photosensitive coating deposited on the insidesurface of said disc and in electrical contact with the inside of saidmetal tubular member for providing within the tube a source ofphotoelectron emission, a collector electrode having a portion sealedwithin said tube for collecting the photoelectron emission from saidcathode.

2. A photoelectric tube including an envelope, said envelope comprisinga glass tubular member, aV metal tubular member of the samecross-sectional area coaxially sealed at one end to one end of saidglass tubular melmber and a transparent window closing the other end ofsaid metal tubular member, a photosensitive coating adhering to theinside surface of said window and in electrical contact with said metaltubular member for providing within the tube a source of photoelectronemission, a collector `electrode closing the other end of said glasstubular member for collecting the photoelectric emission from saidcathode.

3. A photoelectric tube comprising a glass tubular member forming anenvelope portion of the tube, a cathode including a metal tube sealed toone end of said glass tubular member and forming a second envelopelportion of the tube,- a transparent disc closing the other end of saidmetal tube and anvelectrically conducting photosensitive substancecoated on the inner surface of said transparent disc, saidphotosensitive substance extending in electrical contactv with the innerwall of said metal tube for providing within the tube a source ofphotoelectron emission,

an anode electrode within said envelope having a portion sealing thevother end of 'said glas tubular member.

4. A photoelectric tulbe comprising a cylindrical insulating member, acathode electrode including a metal cylinder sealed to one end of saidinsulating cylinder and forming therewith a portion of the envelope ofsaid tube, a glass window closing said metal cylinder and anelectrically conducting photosensitive lm deposited over the innersurface of said glass window, said photosensitive film extending inelectrical contact'with said metal cylinder for providing within thetube a source of photoelectron emission; and an ano'de Y electrode.within said envelope having a `portion sealing the other end of saidcylindrical insulating member. Y.

5. A photoelectric tube including an evacuated envelope, said envelopecomprising a tubular member and a transparent Yphotosensitive cathodeelectrode sealed across one end of said tubular member, an anodeelectrode assembly having a portion spaced within said envelope fromsaid cathode electrode and a metal cup portion sealed across Vthe otherend of said tubular member.

6. A photoelectric tube including an evacuated envelope, said envelopecomprising a hollow cylindrical member and a transparent photosensitivecathode velectrode closing one end of said hollow cylindrical member, ananode electrode assembly havinga Vconductive portion closely spacedwithin said envelope from said cathode electrode and a metal cup portionsealed across the other end of said tubular member.

7. A photoelectric tube including an envelope, said envelope comprisinga glass tubular member, a metal tubular member of the samecrosssectional area coaxially sealed at one end to one end of said glasstubular member and a transparent window closing the other end of saidmetal tubular member, a photosensitive coating deposited on the insidesurface of said window and in electrical contact with the inside of saidmetal tubular member for providing within the tube a source ofphotoelectron emission, a collector electrode comprising a closed metaltube extending through the other end of said glass tubular member inspaced relationship to said photosensitive coating for collecting thephotoelectrons emitted therefrom, and means closing and sealing saidenvelope between said glass tubular member and said closed metal tube.

8. A photoelectric tube comprising a cylindrical insulating member ofuniform diameter, a cathode including a metal cylinder sealed at one endto an end of said cylindrical insulating member and forming therewith aportion of the envelope of said tube, a glass window sealed across toclose the other end of said metal cylinder and an electricallyconducting photosensitive substance deposited over the inner surface ofsaid glass window, said photosensitive substance extending in electricalcontact with the wall of said cylinder for providing within the tube asource of photoelectron emission, an anode including a closed coppertube extending through the other end of said cylindrical insulatingmember into said metal cathode cylinder and in spaced relationship tosaid photosensitive lm for collecting the photoelectrons emittedtherefrom and a metal cup fixed to said copper tube to said cylindricalinsulating member to close said envelope between said cylindricalinsulating member and said enclosed copper tube.

9. A photoelectric tube comprising an evacuated tubular envelope, aphotosensitive cathode electrode closing one end of said tubularenvelope and an anode electrode having one portion spaced within saidenvelope from said cathode electrode and a second portion sealed to andhermetically closing the other end of said tubular envelope.

10. A photoelectric tube comprising an evacuated tubular envelope, aphotosensitive cathode electrode closing one end of said tubularenvelope and an anode electrode including a cylindrical member extendingcoaxially into said tubular envelope and a portion closing the other endof said tubular envelope, said cylindrical anode member extending inspaced relationship to said photosensitive cathode electrode forcollecting the photoelectron emission therefrom, said cylindrical anodemember including a hollow exhaust tubulation for said tubular envelope.

11. A photoelectric tube comprising a tubular envelope, a transparentwindow closing one end of said tubular envelope, a transparentphotosensitive nlm deposited on the inside surface of said window, saidphotosensitive lm forming a photoelectron emitting `cathode adapted tobe activated by a beam oi light passing through said window, acylindrical anode electrode having one end enclosed in said tubularenvelope, said cylindrical anode including a portion closing the otherend of said tubular envelope, the enclosed end of said anode electrodeextending in spaced relationship to said photoelectron emitting cathodefor collecting the photoelectron emission therefrom, said cylindricalanode electrode formed of a hollow metal tube with said enclosed endopen for exhausting said envelope and the other end thereof hermeticallysealed after tube exhaust.

12. A photoelectric tube including an envelope, said envelope comprisinga tubular insulating member and a tubular photosensitive cathodeelectrode coaxially sealed to one end of said tubular insulating member,an anode electrode formed of a hollow metal tube enclosed within saidtubular insulating member, one end of said anode tube extending intosaid tubular photosensitive cathode for collecting the photoelectronemission therefrom, the other end of said anode tube eX- tending throughthe other end of said tubular insulating member, means hermeticallyclosing said envelope between said other end of said tubular insulatingmember and said anode tube, whereby said anode tube forms an exhausttubulation for said photoelectric tube, said other end of said anodetube hermetically closed after tube exhaust.

13 A photoelectric tube including an envelope, said envelope comprisinga tubular insulating member and a photosensitive cathode electrode, saidphotosensitive cathode including a metal cylinder coaxially sealed atone end to an end of said tubular insulating member and a transparentwindow hermetically closing the other end thereof, an anode electrodeformed of a hollow copper tube enclosed within said tubular insulatingmember, one end of said anode tube extending into said photosensitivecathode cylinder for collecting the photoelectron emission therefrom,the other end ci said anode tube extending through the other end of saidtubular insulating member, cup means hermetically closing said envelopebetween said other end of said tubular insulating member and said anodetube, whereby said anode tube forms an exhaust tubulation for saidphotoelectric tube, said other end of said anode tube hermeticallyclosed after tube exhaust, a conductor fixed to said other end of saidanode tubulation for connecting said photoelectric tube in a circuit.

RALPH W. ENGSTROM. WILLIAM J. PIETENPOL.

REFERENCES CITED The following references are of record in the i-lle ofthis patent:

UNITED STATES PATENTS Number Name Date 1,893,887 Giard Jan. 10, 19331,945,979 Parker Feb. 6, 1934 2,123,412 Gardner July 12, 1938

